Mobile social software norms

An interesting news on the Foursquare newsblog is about the "cheater code", i.e. a way to catch users who check in from their couches to steal mayorships. Interestingly, it seemed to be one of the most requested feature by people.
Of course, it's not that easy to implement and the solution that has been chosen... lies in using the phone’s GPS (or another way to get the user's location) "to try to verify this". What I find interesting here is that the ambition is deliberately low (hence the "try"). The reasons why they do so are simply that it's hard:

" We are seeing some issues where people should be getting points / badges / mayors but they’re not. This could be because the GPS location your phone gave us was slightly off or because the address / pushpin where we located the venue wasn’t quite right."

Another valuable bit reveals a lot about the usage/norms about what is considered acceptable:

"Also worth noting that we’re fine with pre-checkins and post-checkins… you know, the checkins you send *before* you’re at a place (“I’ll be there in 10 mins!”) and the checkins you send us *after* you leave when you realize you forgot to check-in while you were there. (Trust us, we do it too to fill out our history pages!) The only difference now is that to unlock foursquare rewards - mayors, points, badges, etc - those checkins needs to be sent from that place."

Why do I blog this? I am fascinated by this kind of elicitation as it uncovers norms and behavioral issues that people put in place when using location-based services. Preparing a field study about the usage of this platform, I find interesting to take this into account.